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Caenorhabditis elegans" locomotion consists of long forward crawling interrupted by short spontaneous reversals. We identified several intrinsic and extrinsic variables that influence the reversal frequency. In particular, reversal frequency can be transiently suppressed by touch. The genes glr-1 and nmr-1, which encode subunits of AMPA- and NMDA-type glutamate receptors, play a central role in touch-induced reversal suppression. Thus, reversal behavior is a motor output reflecting the integration of sensory inputs that display a form of memory. Food has a dramatic effect on reversal frequency that depends on chemosensation. Wild-type worms dramatically reduce reversal frequency on food but chemosensory mutants do not. A null allele of eat-2, a gene necessary for the proper response to food, confers a hyperreversal phenotype. eat-2 also enhances dauer formation in a serotonin deficient genetic background. These phenotypes do not appear to result from the effect of eat-2 on eating efficiency.

No description available.